1. Field of the Invention
The present invention relates generally to electrical contacts and to a method and apparatus for making the contacts. More particularly, the invention concerns a method and apparatus for making four sided electrical contacts of the character having specially configured, spaced apart spring like tines.
2. Discussion of the Invention
Fork like electrical contacts are well known in the art and are widely used in a number of different kinds of electrical applications. Typically, the prior art fork contact includes a pair of inwardly biased sides or tines that extend out from a base so that a member such as a pin contact may be inserted between the pair of sides to make an electrical connection therewith.
Because of the extensive use in industry of electrical contacts of the character described in the previous paragraph, various methods have been suggested in the past for the high volume manufacture of the electrical contacts. In one common prior art method the contact members are stamped or lanced from a suitable piece of sheet material and the contact tongues or tines are then formed or coined as necessary. Exemplary of such electrical contacts is those disclosed in U.S. Pat. No. 3,286,220 issued to Marley et al. and in U.S. Pat. No. 3,812,452 issued to Sturm.
Another prior art method of making electrical contacts involves the splitting of a bar of electrically conductive metal longitudinally over a portion of its length to form two contact tongues. Such a method is described in U.S. Pat. No. 4,040,177 issued to Beeler et al. In one form of the Beeler et al. method, a portion of the bar to be split is to be enclosed between two tools. The tools are then moved, sliding along each other perpendicular to the longitudinal dimension of the bar in mutually opposed directions over a distance which is sufficient to produce the desired splitting. In another method of splitting, the bar to be split is retained over its length such that one end is free to receive a wedge which is longitudinally driven into the bar through this free end.
Experience has shown that, in order to repeatedly produce precision electrical contacts by splitting or shearing the material, it is absolutely essential that the portion of the material immediately adjacent the boundary of the split or shear be rigidly and positively contained. Only in this way can a predictable controlled, precise split of the material be achieved.
An elegantly simple prior art method and apparatus for producing two sided precision electrical contacts by a shearing method is disclosed in U.S. Pat. Nos. 4,909,763 and 4,970,782 issued to the present inventor. In the practice of the methods disclosed in these patents, the starting material from which the electrical contacts are made is closely constrained within the area of the shear boundaries so that predictable and precisely controlled shearing of the material can be repeatably achieved with great accuracy. The present invention comprises an improvement upon the method and apparatus disclosed in U.S. Pat. No. 4,909,763 and in U.S. Pat. No. 4,970,782 and, for this reason, these patents are hereby incorporated by reference as though fully set forth herein.
As will be better understood from the discussion which follows, the thrust of the present invention is to improve on the techniques described in the previously mentioned, incorporated by reference patents and in so doing to provide a method and apparatus for the high volume production of four sided electrical contacts from a starting material which comprises a plurality of spaced apart, pre-cut pins which are precisely split to form four, spaced apart tines or tongue like members. The apparatus of the present invention then forms these four tongue like members into precisely configured, four sided contacts.